Decoherence is a fundamental physical phenomenon which occurs in a variety of quantum systems. It has recently emerged as a priority research topic in many fields of science and technology. This Workshop is intended to bring together international experts from various disciplines, to discuss foundational issues and to explore new research horizons. Our focus will be on decoherence mechanisms in solid-state, atom/molecular and photonic systems, and on quantum algorithms for mitigating decoherence effects in quantum information processing.